High-Pressure Studies of 4-Acetamidobenzenesulfonyl Azide: Combined Raman Scattering, IR Absorption, and Synchrotron X-ray Diffraction Measurements.

We have reported the high-pressure behavior of 4-acetamidobenzenesulfonyl azide (C8H8N4O3S, 4-ABSA) by in situ Raman scattering, IR absorption, and synchrotron angle-dispersive X-ray diffraction (ADXRD) measurements in diamond anvil cells with the pressure up to ∼13 GPa at room temperature. All of the fundamental vibrational modes of 4-ABSA at ambient pressure were analyzed by combination of experimental measurements and theoretical calculations using the density functional theory method. Detailed Raman and IR spectroscopic analyses reveal two phase transitions in the pressure region of 0.8-2 and 4.2 GPa, respectively, which are confirmed by the changes in the ADXRD patterns. The first phase transition in the pressure region of 0.8-2 GPa is attributed to the ring distortion and the rotation of CH3 group, whereas the second phase transition at 4.2 GPa might be induced by the rearrangement of azide group and hydrogen bonds. The analyses of the N3 vibrational modes suggest that the bent azide group rotates progressively upon compression, which is ascribed to the compression of the unit cell along the b axis. This study is helpful to understand the behavior of azide group and structural evolution of 4-ABSA under high pressure.